The present invention relates to a connecting device for pipes conducting pressure medium, having a sleeve-like insert part which can be inserted in a frictional and/or form-fitting manner into a connecting opening in a connecting body (for example, any desired assembly part or housing part) and surrounds a receiving opening for a pipe to be inserted, a sealing element for producing a seal between the connecting body and the pipe, a resilient, essentially annular holding element with holding arms which extend radially inward into the receiving opening, are distributed over the circumference and act in a barb-like manner against the outer circumference of the pipe, and in particular having a release sleeve which engages displaceably in the insert part in such a manner that by pushing in the release sleeve, the holding element can be deformed elastically for the purpose of releasing the pipe.
A device of this type is disclosed in EP 0 616 161 B1. In this case, the holding element is designed as a toothed ring having a multiplicity of radial, tooth-like small holding arms which are connected to one another via peripheral connecting sections. The intention in this known design is to make provision for each peripheral connecting section to be deformable elastically in a narrow point formed within the insert part, with the result that each tooth itself is not deformed per se when the pipe is plugged in, but can pivot around each of the two adjacent peripheral connecting sections. This design consequently results in the toothed ring being mounted in a moveable manner, i.e. in a manner ensuring a conscientious clearance for movement, in its outer circumferential region. However, this mobility leads to the disadvantage that the pipe to be inserted has to be cut off at the end at relatively precisely right angles so that the toothed ring is deformed uniformly over the circumference when said pipe is plugged in. An obliquely cut off pipe could, on account of said clearance for movement, lead to the toothed ring tilting and therefore to problems when the pipe is plugged in.
EP 0 160 559 B1 also describes a similar pipe connection, in which a toothed or serrated ring is likewise mounted moveably just in its outer circumferential region too.
The invention is based on the object of providing a pipe-connecting device of the type mentioned, which ensures good and reliable securing of the pipe and improved insertion and operating characteristics when plugging the pipe in and also when releasing it, with the entire, fitted device and also its individual parts being of simple and inexpensive design.
According to the invention, this is achieved in that the holding element is held, by an outer circumferential region, in an essentially clearance-free manner axially, as seen in the direction of the plug-in axis of the pipe, relative to the insert part, with the result that elastic deformation takes place in the region of the holding arms when inserting or releasing the pipe.
According to the invention, the holding element is therefore held in a defined manner in particular in its outer circumferential region, specifically at least in the axial direction. There is no clearance in the axial direction or there is only a slight clearance to the effect that tilting of the entire holding element is thereby virtually ruled out in the outer circumferential region. The connecting device according to the invention is therefore advantageously also suitable for obliquely cut off pipe ends, because the holding arms can also be deformed independently of one another, i.e. also successively or in each case in a different manner, by the respective pipe end until said holding arms then all act equally against the outer circumference of the pipe. A readily definable holding function is then also achieved. In addition, a very thin and therefore cost-effective material (spring steel sheet) for the holding element can advantageously also be used on account of the securing in an essentially clearance-free manner axially.
The holding element can likewise be held in a clearance-free manner in the radial direction, i.e. transversely with respect to the insertion axis. However, a radial clearance for movement (sliding fit) may also be advantageous because self-centering of the holding element is thereby achieved when the pipe is plugged in.